Chemical Composition of Deep-Sea Manganese Nodules from the Pacific Ocean

Chemical analyses of acid-soluble fraction on eight Pacific manganese nodules are described so as to find chemical characters with a special interest in their growth at the deep sea floor, using atomic absorption spectrophotometry, in which a newly developed procedure for rough estimate followed by precise determination of metals is used. The definitely negative correlation between Mn and Fe contents was found, which supports the alternative structural enrichments in manganese nodules. Strong positive correlation between Cu or Ni and Mn contents, and strong negative correlation between Cu or Ni and Fe contents were also noticed. The fact that no clear correlation between Co and Mn or Fe contents was presented, could explain the lack of selectivity in acid leaching of Co from the manganese nodules. Data for chemical analyses of acid-insoluble fraction showed that SiO_2 contents were nearly constant over the range of 82-89% independent of their origin, and Al_2O_3 contents amounted to 4.8-9.4%, both of which might take part in the formation of alumino-silica gel as well as the inclusions of foreign minerals such as quartz or plagioclase during the growth of the deep-sea manganese nodules.